This application proposes the continued operation of the Central Pathology Laboratory which has been established for the review of cytologic and pathologic material from institutions participating in the research activities of Clinical Collaborative Group A of the National Bladder Cancer Project. Both qualitative and quantitative microscopic assessment of submitted material will be carried out by cytotechnologists and pathologists, and the result will be correlated with clinical data during the follow-up period of this prospective study. The ultimate intent of the project is to develop improved means of classifying individual patients for treatment.